1. Field of the Invention
The present invention relates to a semiconductor device mounting jig and a method of mounting a semiconductor device, more particularly relates to a method of mounting a semiconductor device having a package form made to be compact and high density and a semiconductor device mounting jig used therefor.
2. Description of the Related Art
Demand for more compact, thinner, and lighter digital video cameras, digital cellular phones, laptop personal computers, and other portable electronic devices has been increasing steadily. To meet the demand, a 70% reduction in three years has been realized and smaller sizes and high performance have been achieved in recent VLSIs and other semiconductor devices.
Along with the higher performance of semiconductor devices, semiconductor device packages have been made smaller and higher in number of pins. There has been a shift from the conventionally broadly used dual inline packages (DIP) and other through hole mount devices (THD) inserting leads into through holes formed in a printed board to quad flat (L-leaded) packages (QFP) and other surface mount devices (SMD) mounted by soldering lead terminals on the surface of a board and further to ball grid array (BGA) packages with output terminals provided at areas on the bottom surface.
Further, a package called a chip size package (CSP), also called a fine-pitch BGA (FBGA), having terminals on its bottom surface, making the package size close to the size of the semiconductor chip, and realizing further compactness and higher density has been developed and put into broad use up to now.
As the method of mounting a semiconductor chip of the above CSP format, flip-chip mounting for directly mounting a bare LSI chip with the pad opening surface side facing to the mounting board or mounting an LSI chip to a buffer base called an xe2x80x9cinterposerxe2x80x9d to make a CSP and mounting this on a mounting board has come into note.
In flip-chip mounting, the LSI chip is provided with projecting electrodes such as gold stud bumps and solder bumps.
Flip-chip mounting using solder bumps enables simultaneous mounting of a large number of LSI chips when using reflow of the solder bumps, so the productivity is extremely high. Also, compared with connection using gold stud bumps, there is the advantage that bonding with a low load is possible.
Generally, in flip-chip mounting using reflow of the solder bumps, a rigid substrate comprised of glass-epoxy etc. is used.
On the other hand, flip-chip mounting may also be conducted using a flexible tape substrate formed by processing polyimide or another insulating resin to a tape shape and having the advantage of being thin and light weight.
However, since a flexible tape substrate is more flexible than a rigid substrate, a flexible tape substrate easily flexes in the process of mounting an LSI chip by flip-chip mounting, therefore easily suffers from problems in connection of the solder bumps described below.
When, for example as shown in FIG. 9, mounting a semiconductor device 5 comprised of an LSI chip 50, electrodes 51 connected to its pads, and solder bumps 52 formed on the electrodes, on to a flexible tape substrate comprised of a highly flexible substrate 40 on which lands (electrodes) 41a are formed, if mounting by reflow of the solder bumps while the flexible tape substrate 4 is left flexed, unconnected portions U arise between the solder bumps 52 and lands 41a, and alternatively, in the case of a semiconductor having a narrow pitch between adjacent solder bumps, bridges B occur between adjacent solder bumps and other problems arise easily in solder bump connection.
To prevent the above disadvantages in solder bump connection, it is necessary to keep the flexible tape substrate flat during especially narrow pitch flip-chip soldering by reflow.
As a method of reflow while keeping the flexible tape substrate flat, a method of affixing the flexible tape substrate on a holding base using an adhesive tape (see Japanese Unexamined Patent Publication (Kokai) No. 8-222820) and a method of forming through holes in the flexible tape substrate in advance and affixing the flexible tape substrate by fitting them over projections formed on the holding base (see Japanese Unexamined Patent Publication (Kokai) No. 8-254996) have been proposed.
The above two methods, however, have disadvantages that the area for holding the flexible tape substrate is small, the holding force is weak, and the flexible tape substrate sometimes comes off from the holding base.
Also, a method of affixing the flexible tape substrate on the holding base by an adhesive or two-sided adhesive tape may be considered.
In this case, however, at the time of release, that is, detaching the flexible tape substrate from the holding base, stress ends up being imposed on the semiconductor device. The semiconductor device is liable to be damaged in some cases.
An object of the present invention is to provide a semiconductor device mounting jig capable of stably holding a flexible tape substrate flat in a process of mounting a semiconductor device on the flexible tape substrate by flip-chip mounting and not applying stress to the semiconductor device at the time of release and a method of mounting a semiconductor device mounted on a flexible tape substrate by using the semiconductor device mounting jig.
To attain the above object, according to a first aspect of the present invention, there is provided a semiconductor device mounting jig for holding a mounting board flat when mounting a semiconductor device on the mounting board, comprising a holding plate having a flat mounting board holding surface; suction holes penetrating through the holding plate at the mounting board holding surface; and a suction means for applying suction at the suction holes from an opposite side to the mounting board holding surface; suction being applied at the suction holes while the mounting board is placed on the mounting board holding surface so as to hold the mounting board by suction.
Preferably, the holding plate is fit into an opening of a plate support having a hollow portion inside it and the opening communicated with the hollow portion and the suction means applies suction to the hollow portion to apply suction at the suction holes from the opposite side to the mounting board holding surface.
Preferably, a suction nozzle communicating with the hollow portion is provided at the plate support; and a suction pump is connected to the suction nozzle to apply suction to the hollow portion.
More preferably, a valve for opening and shutting the suction nozzle is provided at the suction nozzle; and the suction pump can be attached to or removed from the suction nozzle.
Preferably, the holding plate and the plate support are made as one body.
Preferably, the holding plate is fit into the opening of the plate support through an O-ring.
That is, the above semiconductor device mounting jig of the present invention comprises a holding plate having a flat mounting board holding surface integrally formed at an opening of a plate support having a hollow portion inside it and the opening communicated with the hollow portion or fitted in the opening of the plate support through an O-ring, suction holes in the mounting board holding surface penetrating through the holding plate, and a suction means for applying suction at the suction holes from the opposite side to the mounting board holding surface such as applying suction at the hollow portion of the plate support.
Accordingly, by placing a mounting board on the mounting base holding surface while applying suction from the suction holes, the flexible tape substrate is held by suction and kept flat and stable in the process of mounting a semiconductor device on a flexible tape substrate by flip-chip mounting etc. Further, the hold can be easily released by releasing suction to return to a normal pressure, so no stress is imposed on the semiconductor device.
Further, when configured so that a valve is provided at the suction nozzle and a suction pump can be attached to or removed from the suction nozzle, after holding the mounting board on the mounting board holding surface, the mounting board can be kept held even if the suction pump is removed from the suction nozzle by closing the valve of the suction nozzle.
According to a second aspect of the present invention, there is provided a method of mounting a semiconductor device, comprising steps of placing a mounting board on a flat mounting board holding surface of a semiconductor device mounting jig comprising a holding plate having the mounting board holding surface, suction holes penetrating through the holding plate at the mounting board holding surface, and a suction means for applying suction at the suction holes from an opposite side to the mounting board holding surface, and applying suction at the suction holes to hold the mounting board; placing a semiconductor device on the mounting board; and connecting the semiconductor device to the mounting board.
Preferably, a flexible tape substrate comprising a substrate made of an insulating resin processed to form a tape shape and formed with an interconnection pattern is used as the mounting board; in the step of placing the semiconductor device, the semiconductor device is placed so that bumps formed previously on the semiconductor device contact the interconnection pattern; and in the step of connecting the semiconductor device to the mounting board, the bumps are connected to the interconnection pattern.
Preferably, in the step of connecting the semiconductor device to the mounting board, the semiconductor device is connected with solder to the mounting board.
More preferably, in the step of connecting the semiconductor device to the mounting board, the semiconductor device is connected to the mounting board by reflow of the solder.
Preferably, the method further includes, after connecting the semiconductor device to the mounting board, a step of injecting a sealing resin in a gap between the mounting board and the semiconductor device in the state holding the mounting board on the mounting board holding surface of the semiconductor device mounting jig and a step of hardening the sealing resin to seal the gap between the mounting board and the semiconductor device in the state holding the mounting board on the mounting board holding surface.
That is, the method of mounting a semiconductor device of the present invention places on the mounting board holding surface of a semiconductor device mounting jigxe2x80x94provided with a holding plate having a flat mounting board holding surface, suction holes penetrating through the holding plate at the mounting board holding surface, and a suction means for applying suction at the suction holes from the opposite side to the mounting board holding surfacexe2x80x94a flexible tape substrate or other mounting board comprising a substrate comprised of an insulating resin formed to a tape shape and formed with an interconnection pattern and applies suction from suction holes so as to hold the mounting board.
Next, a semiconductor device is mounted on the mounting board while bringing bumps formed in advance on the semiconductor device to contact with the interconnection pattern of the mounting board.
Then, the semiconductor device is connected to the mounting board by connecting the interconnection pattern etc. to the bumps by reflow etc.
According to the method of mounting a semiconductor device of the present invention, by placing a mounting board on the mounting board holding surface while applying suction at suction holes, it is possible to apply suction to a flexible tape substrate or other mounting board to hold it flat and stable and to mount a semiconductor device on the mounting board by flip-chip mounting etc. Also, by releasing the suction to return to a normal pressure, the hold can be released without imposing any stress on the semiconductor device.
Furthermore, by injecting a sealing resin in the gap between the mounting board and the semiconductor device in the state holding the mounting board on the mounting board holding surface and hardening the sealing resin, it is possible to seal with resin in the state holding the flexible tape substrate or other mounting board flat and stable.